Implantable surgical marker

ABSTRACT

An implantable marker for implantation in tissue of a surgical patient is disclosed. The marker has a base and an elevated bridge. A pair of legs descend from first and second transitions of the bridge. Each leg has a distal tip, a generally straight leg arm adjacent the tip, and a camming marker surface between the transitions of the base and the straight leg arm. The camming marker surfaces extend outwardly from the straight leg arms of the legs. In its open configuration, the first and second straight leg arms of the legs of the marker are generally parallel to each other. In its closed configuration, the first and second straight leg arms converge towards each other, and a marker apex is formed at the distal tips of the legs. The marker is particularly adapted for fixation in tissue to mark the site of a lesion or other abnormal tissue which may be removed during a biopsy procedure, for example a breast biopsy procedure. Advantageously, the camming marker surfaces of the legs of the marker facilitate the ability to form the marker upon pushing the marker distally into the tissue, thus insuring deep penetration of the marker and the grasping of a sufficient amount of tissue to securely fix the marker to the tissue.

BACKGROUND OF THE INVENTION

This invention relates to a marker for implantation in tissue of asurgical patent. More specifically, it relates to an implantable markerfor defining particular locations in human tissue, particularly in ahuman breast.

One in nine American women will develop breast cancer in their lifetime.It is the leading cause of cancer deaths in women 40-55 years of age andthe second leading cause of cancer deaths in women overall. Breastcancer will be diagnosed in approximately one in eight women in theirlifetime, and one in 30 will die of this disease. Breast cancer doesoccur in males but is much less common. Biopsy requests stem from ascreening process generally performed via a physical examination(palpable) and/or mammogram (non-palpable). A biopsy is indicated ifsuspicious tissue is detected. Five out of six biopsies performed returnbenign indications.

It is desirable and often necessary to perform procedures for detecting,sampling, and testing lesions and other abnormalities in the tissue ofhumans and other animals, particularly in the diagnosis and treatment ofpatients with cancerous tumors, pre-malignant condition and otherdiseases or disorders. Typically, in the case of cancer, when aphysician establishes by means of known procedures (i.e. palpation,x-ray, MRI, or ultrasound imaging) that suspicious circumstances exist,a biopsy is performed to determine whether the cells are cancerous.Biopsy may be an open or percutaneous technique. Open biopsy removes theentire mass (excisional biopsy) or a part of the mass (incisionalbiopsy). Percutaneous biopsy on the other hand is usually done with aneedle-like instrument and may be either a fine needle aspiration (FNA)or a core biopsy. In FNA biopsy, very small needles are used to obtainindividual cells or clusters of cells for cytologic examination. Thecells may be prepared such as in a Papanicolaou (Pap) smear. In corebiopsy, as the term suggests, a core or fragment of tissue is obtainedfor histologic examination, which may be done via a frozen section orparaffin section. The chief difference between FNA and core biopsy isthe size of the tissue sample taken. An imaging system havingspectroscopic capabilities, such as the stereotactic guidance systemdescribed in U.S. Pat. No. 5,240,011 is employed to guide the extractioninstrument to the lesion.

Depending on the procedure being performed, the sample may result in thesuspicious lesion being partially or completely removed. Visibility ofthe lesion by the imaging system may be hampered because of thedistortion created by the extraction process itself as well asassociated bleeding in the surrounding tissues. Although the lesion isremoved and all fluids are continuously aspirated from the extractionsite, it is likely that the process will "cloud" the lesion, thusimpairing exact recognition of its margins. This makes it difficult toensure that the entire lesion will be removed.

Often, the lesion is merely a calcification derived from dead abnormaltissue, which may be cancerous or pre-cancerous, and it is desirable toremove only a sample of the lesion, rather than the entire lesion, toevaluate it. This is because such a lesion actually serves to mark ordefine the location of adjacent abnormal tissue, so the physician doesnot wish to remove the entire lesion and thereby lose a critical meansfor later relocating the affected tissue. One of the benefits to thepatient from core biopsy is that the mass of the tissue taken is small.However, oftentimes, either inadvertently or because the lesion is toosmall, the entire lesion is removed for evaluation, even though it isdesirable to remove only a portion. Then, if subsequent analysisindicates the tissue to be malignant (malignant tissue requires removal,days or weeks later, of tissue around the immediate site of the originalbiopsy), it is difficult for the physician to determine the preciselocation of the lesion, in order to perform necessary additionalprocedures on adjacent potentially cancerous tissue. Additionally, evenif the lesion is found to be benign, there will be no evidence of itslocation during future examinations, to mark the location of thepreviously removed calcification so that the affected tissue may becarefully monitored for future reoccurrence.

Thus, it would be of considerable benefit to be able to permanently markthe location or margins of such a lesion prior to or immediately afterremoving the sample. Marking prior to removal would help to ensure thatthe entire lesion is excised, if desired. Alternatively, if the lesionwere inadvertently removed in its entirety, marking the biopsy siteimmediately after the procedure would enable re-establishment of itslocation for future identification.

A number of procedures and devices for marking and locating particulartissue locations are known in the prior art. For example, location wireguides, such as that described in U.S. Pat. No. 5,221,269 to Miller etal, are well known for locating lesions, particularly in the breast. Thedevice described by Miller comprises a tubular introducer needle and anattached wire guide, which has at its distal end a helical coilconfiguration for locking into position about the targeted lesion. Theneedle is introduced onto the breast and guided to the lesion site usingan imaging system of a known type, for example, x-ray, ultrasound ormagnetic resonance imaging (MRI), at which time the helical coil at thedistal end is deployed about the lesion. Then, the needle may be removedfrom the wire guide, which remains in a locked position distally aboutthe lesion for guiding a surgeon down the wire to the lesion site duringsubsequent surgery. While such a location system is effective, it isobviously intended and designed to be only temporary, and is removedonce the surgery or other procedure has been completed.

Other devices are known for marking external regions of a patient'sskin. For example, U.S. Pat. No. 5,192,270 to Carswell, Jr. discloses asyringe which dispenses a colorant to give a visual indication on thesurface of the point at which an injection has or will be given.Similarly, U.S. Pat. No. 5,147,307 to Gluck discloses a device which haspatterning elements for impressing a temporary mark in a patients skin,for guiding the location of an injection or the like. It is also knownto tape or otherwise adhere a small metallic marker, e.g. a 3 millimeterdiameter lead sphere, on the skin of a human breast in order todelineate the location of skin calcifications (see Homer et al, TheGeographic Cluster of Microcalcifications of the Breast, Surgery,Gynecology, & Obstetrics, December 1985). Obviously, however, none ofthese approaches are useful for marking and delineating internal tissueabnormalities, such as lesions or tumors.

Still another approach for marking potential lesions and tumors of thebreast is described in U.S. Pat. No. 4,080,959. In the describedprocedure, the skin of the portion of the body to be evaluated, such asthe breasts, is coated with a heat sensitive color-responsive chemical,after which that portion of the body is heated with penetratingradiation such as diathermy. Then, the coated body portion is scannedfor color changes which would indicate hot spots beneath the skinsurface. These so-called hot spots may represent a tumor or lesion,which does not dissipate heat as rapidly because of its relatively poorblood circulation (about 1/20 of the blood flow through normal bodytissue). This method, of course, functions as a temporary diagnostictool, rather than in a permanent means for delineating the location of atumor or lesion.

A method of identifying and treating abnormal neoplastic tissue orpathogens within the body is described in U.S. Pat. No. 4,649,151 toDoughety et al. In this method, a tumor-selective photosensitizing drugis introduced into a patient's body, where it is cleared from normaltissue faster than it is cleared from abnormal tissue. After the drugclears normal tissue but before it has cleared abnormal neoplastictissue, the abnormal neoplastic tissue may be located by theluminescence of the drug within the abnormal tissue. The fluorescencemay be observed with low intensity light, some of which is within thedrug's absorbency spectrum. Once detected, the tissue may be destroyedby further application of higher intensity light having a frequencywithin the absorbency spectrum of the drug. Of course, this method alsois only a temporary means for marking the abnormal tissue. Additionally,once the abnormal tissue has been destroyed during treatment, the markeris destroyed as well.

It is also known to employ biocompatible dyes or stains to mark breastlesions. First, a syringe containing the colorant is guided to adetected lesion, using an imaging system. Later, during the extractionprocedure, the surgeon harvests a tissue sample from the stained tissue.However, while such staining techniques can be effective, it isdifficult to precisely localize the stain. Also, the stains aredifficult to detect flouoroscopically and may not always be permanent.

Additionally, it is known to implant markers directly into a patient'sbody using invasive surgical techniques. For example, during a coronaryartery bypass graft (CABG), which of course constitutes open-heartsurgery, it is common practice to surgically apply one or more metallicrings to the aorta at the site of the graft. This enables a practitionerto later return to the site of the graft by identifying the rings, forevaluative purposes. It is also common practice to mark a surgical sitewith staples, vascular clips, and the like, for the purpose of futureevaluation of the site.

A technique has been described for the study of pharyngeal swallowing indogs, which involves permanently implanting steel marker beads in thesubmucosa of the pharynx (S. S. Kramer et al, A Permanent RadiopaqueMarker Technique for the Study of Pharyngeal Swallowing of Dogs,Dysphagia, Vol. 1, pp.163-167, 1987). The article posits that theradiographic study of these marker beads during swallowing on manyoccasions over a substantial period of time provides a betterunderstanding of the pharyngeal phase of deglutition on humans. In thedescribed technique, the beads were deposited using a metallic needlecannula having an internal diameter slightly smaller than the beads tobe implanted. When suction was applied to the cannula, the bead satfirmly on the tip. Once the ball-tipped cannula was inserted throughtissue, the suction was broken, thereby releasing the bead, and thecannula is withdrawn.

Of course, this technique was not adapted or intended to mark specifictissue sites, but rather to mark an entire region or structure of thebody in order to evaluate anatomical movements (i.e. swallowingmotions). It also was not intended for use in humans.

Accordingly, what is needed is a method and device for nonsurgicallyimplanting potentially permanent markers at the site of a lesion orother abnormal tissue, for the purpose of defining the margins of alesion before it is removed and/or to establish its location after ithas been removed. The markers should be easy to deploy and easilydetected using state of the art imaging techniques.

A method of implanting markers directly into a patient's body usingminimally invasive surgical techniques is described in InternationalPatent No. WO 9608208A1 to Foerster et al. In this method, a clippingdevice is introduced to the lesion site by a tubular cannula. Once theclip is at the lesion site, an actuating means at the proximal endoutside the patient deploys the clip into the tissue. This marking meanscan be used long term and can be imaged by most imaging techniques.However, because of its small size, current ultrasound imaging systemsare unable to detect it within the tissue.

Another method of implanting a marker is described in copending,commonly assigned application Ser. No. 08/802,958, filed Feb. 21, 1997,and entitled "Apparatus and Method for Marking Tissue". The markerdescribed in this method utilizes a central tang that is tensely loadedto cause a squarely supported, end contact bridge on the marker to bendresulting in the goal post arms to swing inward in an arcuate fashion topinch tissue. The tensile load on the tang is increased until it breaksat a predetermined location leaving the marker attached to the tissuesite. Unfortunately, this method requires the marker to be pulled awayfrom tissue when the marker is formed, consequently, limiting markerpenetration and the amount of tissue grasped.

A surgical clip for permanently joining opposed tissue for ananastomosis procedure is described in U.S. Pat. No. 4,733,664 to Kirshet al. This is accomplished using an applier, also disclosed, to pull ona frangible central tang to close a pair of spaced arcuate armsextending generally parallel in one direction from opposite ends of theplastically deformable bridge. The arms are brought around opposedtissue. A predetermined force is applied to create a tensile break ofthe neck in the tang. Specific angles of clip shoulder and applier aregiven. The applier jaw faces are in the range of 120° to 180° withrespect to one another, specifically 150°. Unfortunately, the method offorming this clip suffers a fate similar to the method described in thepreceding paragraph.

Accordingly, what is needed is a surgical marker for implantation at thesites of a lesion or other abnormal tissue, for the purpose of definingthe margins of a lesion before it is removed or to establish itslocation after it has been removed. The marker should be easy to deployand easily detected using state of the art imaging techniques.Additionally, the marker must be capable of being formed without themarker being pulled away from the tissue, to ensure that an adequateamount of tissue will be grasped.

SUMMARY OF THE INVENTION

The invention is an implantable marker for implantation in tissue of asurgical patient The marker comprises a base, and first and second legs.

The base of the marker includes an elevated bridge. The bridge isbounded by first and second transitions.

The first leg descends from the first transition of the base. The firstleg includes the following: a) a first distal tip remote from the firsttransition, b) a generally straight first leg arm adjacent the firstdistal tip, and c) a first camming marker surface between the firsttransition of the base and the first straight leg arm. The first cammingmarker surface extends outwardly from the first straight leg arm.

The second leg of the marker descends from the second transition of thebase. The second leg includes the following: a) a second distal tipremote from the first transition, b) a generally straight second leg armadjacent the second distal tip, and c) a second camming marker surfacebetween the second transition of the base and the second straight legarm. The second camming marker surface extends outwardly from thestraight second leg arm.

The first and second straight leg arms are generally parallel to eachother when the marker is in an open configuration. The first and secondstraight leg arms gradually converge towards each other from aspaced-apart position adjacent the first and second transitions when themarker is in a closed configuration. In the closed configuration, amarker apex is formed at the first and second distal tips of the legs.

The marker of this invention is especially adapted for implantation atthe site of a legion or other abnormal tissue particularly during abiopsy procedure to define the margins of a legion before it is biopsiedor to establish its location at some later time after the biopsy samplehas been removed. The configuration of the marker, particularly thecombination of features of the marker with the first and second cammingmarker surfaces of the legs of the marker, facilitate the deployment ofthe marker in a manner in which the marker can be pushed into the tissueduring deployment for deep tissue penetration. Significantly, incontrast to the prior art markers, the deeper penetration of the markerof this invention as it is deployed into tissue enables the marker tograsp a greater amount of tissue, therefore minimizing the potential ofthe marker to unintentionally dislodge.

Although the marker of this invention is particularly suited forendoscopic biopsy applications to mark the site of biopsied tissue, itcan be used for other endoscopic applications and applications involvingconventional open surgical procedures. For example, the marker may findutility in surgical procedures requiring the fastening of tissue or theligation of vessels, such as those surgical procedures which involveclipping, stapling, anastomosis, hernia tacking, buttressing,micro-vascular applications, or any opposed edge joining applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of the implantable marker constructed inaccordance with a preferred embodiment of this invention.

FIG. 2 is a front elevational view of the marker of FIG. 1.

FIG. 3 is a side elevational view of the marker of FIG. 1.

FIG. 4 is a fragmentary distal end sectional view illustrating the planview of the marker of FIG. 1 in its loaded position within the shaft ofan applier.

FIGS. 5-9 are fragmentary distal end sectional views illustratingsequentially the formation of the loaded marker depicted in FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIGS. 1-3, the preferred marker 10 of thisinvention is illustrated. The marker has a base 11 and first and secondlegs, 12 and 13, respectively. The base has an elevated bridge 14. Theelevated bridge has an arcuate bottom surface 15. It also has agenerally flat top 16.

The marker has a first transition 17 on one side of the elevated bridgeand a second transition 18 on the other side of the elevated bridge. Thefirst and second transitions separate the elevated bridge of the basefrom the descending first and second legs of the marker. The first leghas a first, beveled pointed tip 19 at the distal end of the leg remotefrom the first transition 17. Similarly, the second leg has a second,beveled pointed tip 20 at its distal end. Adjacent the first and secondpointed tips of the legs, there are first and second straight leg arms,21 and 22, respectively. Interposed between the first and secondtransitions and the first and second straight leg arms, are first andsecond camming marker surfaces 23 and 24, respectively. The cammingmarker surfaces extend outwardly from the straight leg arms of the legs.The first and second camming marker surfaces have first and secondinterior surfaces, 25 and 26, respectively, which are arcuate inconfiguration.

The marker has first and second reverse cleats, 27 and 28, respectively.The cleats are triangular in configuration. The first cleat protrudesfrom the first camming marker surface and the first transition.Similarly, the second cleat protrudes from the second camming markersurface and the second transition. The cleats protrude generallyparallel to the first and second straight leg arms of the legs.

The bridge of the marker has a pair of top arcuate surfaces, 29 and 30,respectively, separated by the flat top of the bridge on the base of themarker. The first top arcuate surface 29 is bounded by the interiorsurface of the first spike and the surface adjacent the flat top of theelevated bridge. In a similar fashion, the second top arcuate surface 30is bounded by the interior surface of the second spike and the surfaceadjacent the flat top.

The preferred marker is symmetrical about a centerline axis takenthrough the center of the elevated bridge 14 of the base of the marker,and drawn parallel to the first and second straight leg arms, 21 and 22,of the legs. The centerline axis is designated as "L" in FIG. 2. Inaddition, the region of the marker between the flat top of the elevatedbridge and the arcuate bottom surface of the bridge can be characterizedas a bridge flexure region of reduced thickness. The flexure region ofthe elevated bridge increases the flexibility of the marker when it isdeployed from its open position to its closed position, and minimizesthe tendency for the straight leg arms of the legs of the marker tospring back towards their open configuration after formation. Thisincreased flexibility, coupled with the arcuate symmetrical nature ofthe elevated bridge, provides a uniform load on the base of the markerduring marker formation. In its open configuration, the first and secondstraight leg arms of the legs of the marker are generally parallel toeach other.

The first and second reverse cleats of the marker are provided toprevent undesired migration of the formed marker when it is in itsclosed position in tissue by preventing tissue from sliding off of thebridge. Consequently, the surface of the bridge firmly bears againsttissue to prevent undesired migration of the marker.

Referring now to FIGS. 4-9, there is illustrated the deployment of thepreferred marker of this invention from its open configuration to itsclosed configuration. A marker applier 31 is provided which has atubular shaft 32. The marker 10 is positioned inside the tubular shaft.The tubular shaft is sized so that the camming marker surfaces 23 and 24of the legs of the marker contact the shaft inner wall 33 of the tubularshaft. The distal end of the tubular shaft has a distal camming wallsurface 34 extending radially inwardly from the shaft inner-wall. Thedistal camming wall surface is sized so that this surface contacts thefirst and second straight leg arms of the legs of the marker when themarker is in its open configuration, and the leg arms are parallel toeach other as illustrated in FIG. 4. An applier push rod 35 ispositioned on the flat top of the elevated bridge on the base of themarker, and the pointed distal tips of the legs protrude from thetubular shaft of the applier.

When the applier push rod 35 is pushed distally to deploy the markerfrom its open position where the straight leg arms are parallel to eachother to its closed position, the marker is urged out of the tubularshaft of the applier. As the marker moves distally within the tubularshaft of the applier, the camming marker surfaces of the legs of themarker are cammed against the distal camming wall surface of theapplier. This camming action urges the straight leg arms of the legs ofthe marker to converge towards each other as the elevated bridge of thebase of the marker bends inwardly at the bridge flexure region. When themarker is fully formed in its closed position as depicted in FIG. 9, thedistal tips of the legs come together to form a marker apex 36. Thestraight leg arms remain in a spaced-apart position adjacent the firstsecond transitions of the marker, and the marker has formed a generallydiamond-shaped configuration which is illustrated in FIG. 9.

The preferred applier for delivering and deploying the marker of thisinvention is described in detail in commonly assigned, copendingapplication Ser. No. 09/105,570, filed Jun. 26, 1998.

The marker of this invention can be made of any implantable materialwhich is biocompatible and can exhibit the requisite closure force toprevent inadvertent dislodgment of the marker when it is anchored intissue. The preferred marker of this invention is composed of 316 LVMstainless steel (316 L stainless steel fabricated in a vacuum meltfurnace for higher purity).

Alternatively, the marker may be composed of absorbable polymers, aswell as non-magnetic materials particularly suited for MRI imagingapplications.

The marker can be advantageously mass produced using a conventionalphotoetching process to create a plurality of markers affixed to thedesired carriers, typically a sheet of metal composed of 316 LVMstainless steel. The metal sheet can be cut into carrier rows, andsequentially fed into a cutting die for shearing the individual markersfrom the carrier rows.

The marker of this invention can be coated with agents to lowerfriction, stop bleeding or accomplish any other desired effect.Additionally the legs of the marker can be modified to include theaddition of barb-like features that could increase the holding strength,migration resistance and imaging ability of the marker.

Although this invention has been described in connection with its mostpreferred embodiment, additional embodiments are within the scope andspirit of the claimed invention. The preferred marker of this inventionis intended merely to illustrate the invention, and not limit the scopeof the invention as it is defined in the claims which follow.

What is claimed is:
 1. An implantable marker for implantation in tissueof a surgical patient, said marker comprising:a) a base, said baseincluding an elevated bridge having a top and a pair of top arcuatesurfaces separated by said top, said bridge bounded by first and secondtransitions; b) a first leg descending from said first transition ofsaid base, said first leg including:i) a first distal tip remote fromsaid first transition; ii) a generally straight first leg arm adjacentsaid first distal tip; and iii) a first camming marker surface betweensaid first transition of said base and said first straight leg arm, saidfirst camming marker surface extending outwardly from said firststraight leg arm; c) a second leg descending from said second transitionof said base, said second leg including:i) a second distal tip remotefrom said second transition; ii) a generally straight second leg armadjacent said second distal tip; and iii) a second camming markersurface between said second transition of said second base and saidsecond straight leg arm, said second camming marker surface extendingoutwardly from said second straight leg arm; and d) a first reversecleat protruding from said first camming marker surface and said firsttransition, and a second reverse cleat protruding from said secondcamming marker surface and said second transition; wherein said firstand second straight leg arms are generally parallel to each other whensaid marker is in an open configuration, and said first and secondstraight leg arms gradually converge towards each other from aspaced-apart position adjacent said first and second transitions whensaid marker is in a closed configuration so as to form a marker apex atsaid first and second distal tips of said legs.
 2. The implantablemarker of claim 1 wherein said marker is symmetrical about a centerlineaxis drawn parallel to said first and second straight leg arms and takenthrough the center of said elevated bridge of said base of said marker.3. The implantable marker of claim 2 wherein said marker has adiamond-shaped configuration in the closed position.
 4. The implantablemarker of claim 3 wherein said first and second distal tips of said legsare beveled pointed tips.
 5. The implantable marker of claim 4 whereinsaid elevated bridge has an arcuate bottom surface.
 6. The implantablemarker of claim 5 wherein said top of said elevated bridge is agenerally flat top, and said bridge includes a bridge flexure region ofreduced thickness between said flat top and said arcuate bottom surfaceof said elevated bridge.
 7. The implantable marker of claim 6 whereinsaid first and second reverse cleats are generally triangular inconfiguration.
 8. The implantable marker of claim 7 wherein said firstand second reverse cleats protrude generally parallel to said first andsecond straight leg arms of said legs.